Types of disks you can use with Time Machine on Mac
You can use Time Machine with a Time Capsule, and with USB, FireWire and Thunderbolt disks. The disk can be directly connected to your Mac or be on a network. If a disk has partitions, you can use one of the partitions for your backup disk.
Time Machine can’t back up to iPhone, iPad or iPod or to a disk formatted for Windows. If you connect a disk formatted for Windows, it can be reformatted (permanently removing all data) to a Mac format and used as a backup disk.
The most common format for a Time Machine backup disk is Mac OS Extended (Journaled) format, but Time Machine also supports Mac OS Extended (Case-sensitive, Journaled) and Xsan formats.
Important: You can back up from an HFS+ or APFS-formatted disk to an HFS+ disk; however, Time Machine can’t back up to an APFS-formatted disk. If you select a back up disk formatted as APFS, Time Machine offers to reformat it as HFS+.
If the disk uses the Master Boot Record (MBR) partition type, some partitions may not be available for use with Time Machine.
If your backup disk is on a network, the network server can use Server Message Block (SMB) file sharing. Your Mac must be connected to the SMB server when you set up Time Machine. After you select the network disk in Time Machine preferences, Time Machine automatically connects to the disk when it’s time to back up or restore your data.
Note: Some SMB and AFP disks from manufacturers other than Apple don’t support Time Machine. If your network uses an SMB or AFP disk, but the disk doesn’t appear in the list of devices available for Time Machine backups, contact the disk’s manufacturer.